Blastocyst transfer

A blastocyst is an early stage of an embryo that forms about five days after a sperm fertilises an egg. It comprises a cluster of dividing cells and is one step among many on the path to a successful pregnancy. 

During IVF, eggs are removed from your ovaries and mixed with sperm in our state-of-the-art, onsite laboratory so that fertilisation can occur.  The resulting embryos are then left to develop in the laboratory to blastocyst stage before being transferred to your womb.

When the Lister Fertility Clinic first opened in 1988, embryos were routinely transferred back into the womb two to three days after egg collection. We now have the expertise to safely grow embryos for five to six days after egg collection before implanting them in your womb. 

There are four key advantages to this:

1. You have an improved chance of a successful pregnancy. 
The genetic make-up of any embryo becomes more apparent around day 3 of development. By waiting for day 5 or 6 to transfer, we’re able to select the most suitable embryos, helping to improve your chances of having a successful pregnancy. The table below and related chart show how live birth rates are improved for women of all ages when blastocysts are transferred.

Blastocyst transfer - all couples

Age group	All couples	Blastocyst transfer
<35	46.10%	56.00%
35-37	37.30%	48.00%
38-39	27.50%	38.90%
40-42	18.40%	30.00%
43-44	7.10%	16.40%
>44	1.80%	2.40%

 
2. There’s less chance of a multiple pregnancy.
Because we can assess embryo quality more accurately by day 5 or 6, we can also better advise couples about how many to transfer straight away, and which might be suitable for freezing. If you’re under 40 years old, you can legally have no more than two embryos transferred and if you’re 40 years old or over, no more than three.

Younger women with high quality blastocyst embryos are advised to transfer only one as this process does not impact the chance of a positive pregnancy. Any extra high-quality embryos can be frozen.

3. It mirrors the timing of a natural fertilisation process.
When conception happens naturally, eggs and sperm fertilise in the fallopian tube and continue to divide, only reaching the uterus on day 5, at this blastocyst stage. A day 5 or 6 transfer therefore mirrors this natural timing.

4. We can assure embryo quality before freezing
If embryos don’t reach blastocyst stage by day 5 or 6, they won’t have the potential to achieve a pregnancy, so it makes sense to only freeze blastocysts at this point. We recommend only freezing top quality blastocysts to give them a high chance of surviving the freeze and thaw process. Fewer than 90% of blastocysts survive this.

Yes, it does. Because we can assess embryo quality more accurately at day 5, we can better advise you about how many embryos it may be best to transfer straight away. 

• Younger women with high quality blastocyst embryos are advised to transfer only one
• If you’re under 40, you can legally have no more than two embryos transferred
• If you’re 40 or over, no more than three are allowed

Yes, we can. By day 3 of development, the genetic make-up of any embryo becomes more apparent, so by day 5 or 6 we can select the most suitable embryos to transfer. If embryos don’t reach blastocyst stage by then, they won’t have the potential to achieve a pregnancy, so waiting until this stage is a great way to check the quality of your embryos.